Author Topic: Mid- Engine Modified Sports  (Read 784805 times)

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1260 on: March 15, 2017, 09:16:44 PM »
More progress on the spoiler today- lots of drilling & riveting. Made two support struts and mounting brackets as well as brackets to attach both end plates. I put in two 10-32 Rivnuts in each bracket so that the spoiler angle can be adjusted easily. Researched Gurney flap technical data so now I have a good idea of how much adjustment is needed.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1261 on: March 16, 2017, 11:25:12 PM »
 carefully read through some of the JWAE  MIRA wind tunnel test data on a Porsche 917 that John Horsman shared with me. Surprisingly, the optimum down force-to-drag ratio occurred at around 5 degrees incidence. This is much lower than I would have guessed. JWAE ran their 917s on some very fast tracks, such as Le Mans and Spa, where its top speed was close to 240 mph so drag was important as well as down force. Another effect of increasing rear down force is that it creates a lifting moment on the front due to the leverage of the rear spoiler being behind the rear tires. As down force increased, it became more sensitive to yaw angle as well.
 
My research turned up a paper that stated a Gurney flap was most effective (down force-to drag ratio once again) at between 1% and 4% of cord- again, less than I thought.
 
I finished the spoiler this afternoon and laid it in the rear body to see how wide it looked. Both the body and the spoiler are upside down, just lying in there.
 
Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Online tauruck

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Re: Mid- Engine Modified Sports
« Reply #1262 on: March 17, 2017, 01:56:38 AM »
On the F2 car the Gurney tab was only about 15mm tall and when you used it, it definitely had a big effect.
Probably the simplest, cheapest go fast goodie in aero. It works. :cheers:

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1263 on: March 17, 2017, 07:46:36 PM »
 Today I got as far as putting the spoiler pieces in place to see how everything fits together. There is lots more to do- but I'll save that for tomorrow.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1264 on: March 21, 2017, 07:20:58 PM »
I finished all the metalwork on my spoiler this morning and set up a couple of sawhorses outside to spray on a two-part zinc chromate epoxy primer like I used on my chassis. I wiped down everything with denatured alcohol to get it squeaky clean and got out my paint gun. When I opened "Part B", it was set up solid  :x there goes that idea. I did have a couple of spray cans of primer- one zinc chromate and the other a SEM self-etching gray. Unfortunately, both cans were close to being empty. Plunge ahead, regardless....

I sprayed the spoiler gray and the end plates chromate but with a breeze outside and very little primer to work with, the coating wasn't very cosmetic.  :-( It is a 35 mile trip into town to buy more primer so this will have to suffice.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1265 on: March 22, 2017, 08:43:58 PM »
I had to drive into town anyway today to get my little dog, Doc, his rabies shot so I had a chance to restock my supply of primer. I also bought two cans of gloss black enamel. This afternoon I painted my spoiler black- a crummy job, even for a spray can-- but at least it matches the color of the car- black.

I ordered an adjustable HANS yesterday. My driver's position is pretty reclined and there was no fixed device that had an acceptable angle but the adjustable model should work. It should probably arrive on Monday.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Online tauruck

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Re: Mid- Engine Modified Sports
« Reply #1266 on: March 23, 2017, 12:25:05 AM »
The spoiler looks good Neil.
It sucks when one of the parts has cured solid in the can.
BTW, whats going on with the right front fender well?.
Looks like a mold of sorts.

I'd really love to see that HANS device. :cheers:

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1267 on: March 23, 2017, 01:30:39 AM »
I guess it does look peculiar, Mike, but it is just a piece of scrap polyethylene plastic I placed over the RF tire to keep the fiberglass dust off of it while I was cutting out the louvers.

We'll see how the spoiler works-- we'll see.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1268 on: March 25, 2017, 05:11:57 PM »
I've made some progress on my rear spoiler:

I finished mounting my rear spoiler this morning. I decided to make it removable instead of riveting it to the fiberglass so it took lots of 1/4-28 bolts! I measured the spoiler angle at 0, 3, 6, 9, 12, & 15 degrees, marked the hole locations and drilled holes for bolts to set it at those angles. The "zero degree" datum point is the same angle as the slight upsweep of my rear bodywork.

I still need to make a body mounting bracket for each of the two support struts. I'll spread the load over a few square inches with a sandwich plate.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1269 on: March 25, 2017, 05:33:49 PM »
Photo
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1270 on: March 25, 2017, 05:35:02 PM »
Another photo
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1271 on: March 25, 2017, 05:38:47 PM »
Sorry about doing this one photo at a time but right now two or more photos doesn't work.
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1272 on: March 25, 2017, 05:40:04 PM »
Detail
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1273 on: March 25, 2017, 05:41:07 PM »
Mounting
Regards, Neil  Tucson, AZ

Offline jacksoni

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Re: Mid- Engine Modified Sports
« Reply #1274 on: March 25, 2017, 06:45:43 PM »
Neil= as usual just blown away by the quality construction!!! However there is a feature of your spoiler that may run afoul of rule interpretation. That is the sort of tunnel coming off the top of the car to the back that will allow air to pass both above and below the spoiler. As I understand the rule, that makes it a wing, and therefore illegal. I freely admit I may be wrong (hope I am) on this but I think you better ask whoever is the /MS tech person or Dan Warner for an official ruling. :-(
Jack Iliff
 G/BGS-250.235 1987
 G/GC- 193.550 2021
  G/FAlt- 193.934 2021 (196.033 best)
 G/GMS-182.144 2019